Patent Application
20190113228
The invention relates to the field of cylindrical gas premix burners. Such burners include a mixing chamber within the contours of the burner deck; and an inlet to supply premix gas into the mixing chamber.
Cylindrical premix burners are known. The cylindrical burner deck encloses a mixing chamber. An inlet device can be provided for supplying premix gas (combustible gas and air) into the mixing chamber. The gas is combusted after it has flown through the burner deck. The burner deck stabilizes the combustion.
EP2037175A2 discloses a premix burner comprising a perforated tubular body. The body is closed on a head by a plate welded or crimped along its side surface. The burner comprises a disk, fixed to the opposite head of the tubular body. The disk is provided with a plurality of through openings or holes and constitutes the supply and distribution head of the air-gas mixture into the tubular body.
WO13120715A1 and WO13120716A1 disclose cylindrical premix gas burners comprising a cylindrical burner deck. The cylindrical premix gas burner is delimited by an end cap. At the opposite side of the end cap, an inlet disc with perforations is provided for the supply of a premix of combustible gas and air into the burner and which is to be burnt on the outside of the cylindrical burner deck after the premix gas has flown through it.
The inlet disc of the burner of WO13120715A1 comprises a multiple of perforations for premix gas supply in a central zone of the plate, and a multiple of perforations for premix gas supply in the peripheral zone of the inlet disc. The porosity of the inlet disc is higher in the central zone than in a peripheral zone. The average surface area of the perforations in the central zone of the inlet disc is less than 20 mm2.
The inlet disc of the burner of WO13120716A1 comprises a plurality of perforations for supplying premix gas supply into the burner. The inlet disc has a centre point, which is where the central axis of the cylindrical premix gas burner crosses the inlet disc. The inlet disc is not permeable to premix gas at least within a circle with a diameter of at least 8 mm around the centre point.
It is the objective of the invention to provide an improved cylindrical premix gas burner. It is a specific objective of the invention to provide such a burner that can be ignited more easily, and at which flame sensing can be done more easily. It is a specific objective to provide such a burner with a large L/D ratio, wherein L is the axial length of the burner deck and D is the internal diameter of the cylindrical burner deck.
The first aspect of the invention is a cylindrical gas premix burner comprising:
Preferably, each of the perforations in the perforated metal plate is smaller than 20 mm2.
Preferably, the burner is provided for combusting hydrocarbons, e.g. natural gas, methane, butane, propane or LPG.
Burners with a cylindrical burner deck are provided with an igniter (ignition electrode) and frequently also with a flame sensing probe (flame sensing electrode). It is common practice to install the igniter and—if present—the flame sensing probe at the base of the cylindrical burner deck, meaning at the side of the inlet device. Prior art burners have shown problems with ignition (difficult and/or unreliable ignition) and difficult and/or unreliable flame sensing. Surprisingly the burner of the invention provides stable ignition and reliable flame sensing, even when using short length igniters and short length flame sensing probes installed close to or at the inlet side of the burner. Even more surprisingly, the benefits were also present, and even to a larger extent, for cylindrical burners with a large L/D ratio, e.g. with an L/D ratio of more than 3, or even more than 6. For the L/D ratio, L is the axial length of the burner deck and D is the internal diameter of the cylindrical burner deck.
In a preferred embodiment, the dome shape of the perforated metal plate is provided by deep drawing of a perforated metal plate.
Preferably, the shape of the inlet device is axisymmetric around the axis of symmetry of the gas premix burner.
Preferably, the inlet device comprises a flange for mounting the inlet device into the burner. In an embodiment of the invention, the flange and the perforated plate are integrally formed in one shaped metal plate. In an alternative embodiment, the dome shaped perforated metal plate is attached to the flange, e.g. via welding.
In a preferred embodiment, the cylindrical burner deck has an L/D ratio of more than 3, more preferably more than 4, more preferably more than 5, more preferably more than 6. And preferably less than 7. L is the axial length of the burner deck and D is the internal diameter of the cylindrical burner deck.
In a preferred embodiment, the end cap is not permeable to premix gas.
Preferably, the perforated metal plate is double curved at the central axis of the cylindrical burner deck. With double curved is meant that there is no direction in which the radius of curvature at that point is infinite.
Preferably, the perforated metal plate comprises a flat central section provided with perforations. In such embodiment, the perforated metal plate can have a curved segment contacting the flange around the full circumference of the flange, with a flat central section at the inside of the curved segment. The curved segment can e.g. be a spherical segment.
In a preferred embodiment, the perforated metal plate comprises a spherical segment. More preferably, the spherical segment is positioned axisymmetrically in the cylindrical gas premix burner.
In a preferred embodiment, the inlet device comprises a surface for mounting the burner into a heating appliance. The dome shape of the perforated metal plate extends into the inside of the mixing chamber. The largest distance P from the surface of the dome shape of the perforated metal plate to the plane of the surface of the inlet device for mounting the burner into a heating appliance is at least 0.25 times the internal diameter D of the cylindrical burner deck.
In a preferred embodiment, the cylindrical burner deck comprises at its end where the inlet device is provided a blind zone onto which no combustion occurs when the burner is in use. The blind zone is preferably provided as a ring on the cylindrical burner deck. The blind zone has a length L1 measured from the end of the cylindrical burner deck where the inlet device is provided. The inlet device comprises a surface for mounting the burner into a heating appliance. The dome shape of the perforated metal plate extends into the inside of the mixing chamber. The largest distance P from the surface of the dome shape of the perforated metal plate to the plane of the surface of the inlet device for mounting the burner into a heating appliance is at least 0.75 times, even more preferably at least 0.9 times the length L1 of the blind zone.
The blind zone can be realized in a perforated metal sheet burner deck by absence of perforations in the blind zone.
The blind zone can be realized in a burner having a textile fabric as burner deck provided in contact at its inner side with a perforated metal sheet, by absence of perforations in the perforated metal sheet in the blind zone.
Preferably, the cylindrical burner deck comprises or consists out of a perforated metal sheet or of a steel wire mesh. As steel wire mesh, a woven or knitted steel wire mesh can be used.
In a preferred embodiment, the burner deck comprises a perforated metal sheet or a steel wire mesh onto which the flames are stabilized when the burner is in use. When a steel wire mesh is used, the steel wire mesh can be a woven or knitted steel wire mesh. In a more preferred embodiment, the burner is provided so that when the burner is in use, the premix gas flows through the perforated metal sheet of the cylindrical burner deck or through the steel wire mesh of the cylindrical burner deck without further passing through another object once the premix gas has flown through the mesh of the inlet device.
In a preferred embodiment, the cylindrical burner deck comprises a fiber based burner deck. The fiber based burner deck is preferably a metal fiber based burner deck. Preferably, the fiber based burner deck comprises fiber yarns, wherein preferably the fiber yarns comprise a multiple number of fibers in the yarn cross section, preferably metal fibers. The fiber based burner deck can e.g. be a knitted or woven or braided fabric comprising metal fibers or comprising metal fiber yarns, preferably wherein the metal fiber yarns comprise a multiple number of metal fibers in the yarn cross section. Preferably, the burner is provided so that when the burner is in use the flames are stabilized on the surface of the fiber based burner deck.
Preferably, when the cylindrical burner deck comprises a fiber based burner deck, the fiber based burner deck is supported by a perforated metal sheet or by a steel wire mesh. When a steel wire mesh is used, a woven or a knitted steel wire mesh can be used.
A preferred cylindrical gas premix burner is devoid of a diffuser inside the mixing chamber.
A preferred cylindrical gas premix burner is provided so that in use of the burner, the premix gas flows from the inlet device through the cylindrical burner deck without further passing a gas diffusing device.
In a preferred cylindrical gas premix burner, the mixing chamber comprises a diffuser. Preferably, the diffuser comprises or consists out of an open pore cylindrical object, preferably positioned between 1 and 8 mm, more preferably between 1 and 3 mm, from the inside of the cylindrical burner deck, and preferably parallel with it.
In a preferred cylindrical gas premix burner, an ignition pen and/or a flame sensing pen is provided. The ignition pen and/or the flame sensing pen are provided at the side of the burner where the inlet device is provided. Preferably, the ignition pen and/or the flame sensing pen are provided parallel with the axis of the cylindrical burner deck. Preferably, along the burner deck, the length of the ignition pen is less than 20% of the length of the cylindrical burner deck, and more preferably less than 10% of the length of the cylindrical burner deck.
The perforated metal plate comprises a flat central section provided with perforations. In such embodiment, the curved segment 342 can be a spherical segment.
Cylindrical burners have been made with internal diameter D 82 mm and length L 588 mm of the burner deck. The burner deck was a perforated metal plate, with a blind zone with length L1 at the base of the burner deck equal to 23 mm. No gas diffusing device was used in the mixing chamber of the burner. Burner A was a prior art burner with a flat perforated plate inlet disk. Burner B was a burner according to the invention with a dome shaped perforated plate inlet disk, with a largest distance P 22 mm from the surface of the dome shaped perforated inlet disk to the plane of the surface of the inlet disk for mounting the burner into a heating appliance. Ignition of each of the burners was tested 10 times at four different air over gas premix gas ratios. The four different air over gas premix gas ratios are indicated by the CO2 percentage in the combustion gas; respectively 8%, 8.5%, 9% and 9.5%. Table I indicates the number of successful ignitions (each time out of 10 trials). The test results show the improved ignition results of the burners according to the invention, especially when the burners are operating at low CO2 percentages of the combustion gas.
| Number | Date | Country | Kind |
|---|---|---|---|
| 16169655.4 | May 2016 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/060740 | 5/5/2017 | WO | 00 |
